47 lines
1.1 KiB
C#
47 lines
1.1 KiB
C#
namespace PerfectNumbers.Core;
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internal static class DeterministicRandom
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{
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[ThreadStatic]
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private static ulong s_threadState;
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private static long s_seedCounter;
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public static ulong NextUInt64()
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{
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ulong state = s_threadState;
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if (state == 0UL)
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{
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state = InitializeThreadState();
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}
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state ^= state >> 12;
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state ^= state << 25;
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state ^= state >> 27;
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s_threadState = state;
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return state * 2685821657736338717UL;
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}
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public static UInt128 NextUInt128()
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{
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UInt128 high = (UInt128)NextUInt64();
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UInt128 low = (UInt128)NextUInt64();
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return (high << 64) | low;
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}
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private static ulong InitializeThreadState()
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{
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ulong seed = (ulong)Interlocked.Increment(ref s_seedCounter);
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seed += 0x9E3779B97F4A7C15UL;
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seed = (seed ^ (seed >> 30)) * 0xBF58476D1CE4E5B9UL;
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seed = (seed ^ (seed >> 27)) * 0x94D049BB133111EBUL;
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seed ^= seed >> 31;
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if (seed == 0UL)
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{
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seed = 0x9E3779B97F4A7C15UL;
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}
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return seed;
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}
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}
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